/*
 * DocumentProvider.java January 2010
 *
 * Copyright (C) 2010, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.stream;

import org.w3c.dom.Document;
import org.xml.sax.InputSource;

import java.io.InputStream;
import java.io.Reader;

import wx.xml.harmony.xml.dom.DocumentImpl;
import wx.xml.stax.api.parsers.DocumentBuilder;
import wx.xml.stax.api.parsers.DocumentBuilderFactory;
import wx.xml.stax.api.stream.Location;

/**
 * The <code>DocumentProvider</code> object is used to provide event
 * reader implementations for DOM. Wrapping the mechanics of the
 * DOM framework within a <code>Provider</code> ensures that it can
 * be plugged in without any dependencies. This allows other parsers
 * to be swapped in should there be such a requirement.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.stream.DocumentProvider
 */
class DocumentProvider implements Provider {

    /**
     * This is the factory that is used to create DOM parsers.
     */
    private final DocumentBuilderFactory factory;

    /**
     * Constructor for the <code>DocumentProvider</code> object. This
     * is used to instantiate a parser factory that will be used to
     * create parsers when requested. Instantiating the factory up
     * front also checks that the framework is fully supported.
     */
    public DocumentProvider() {
        this.factory = DocumentBuilderFactory.newInstance();
        this.factory.setNamespaceAware(true);
    }

    /**
     * This provides an <code>EventReader</code> that will read from
     * the specified input stream. When reading from an input stream
     * the character encoding should be taken from the XML prolog or
     * it should default to the UTF-8 character encoding.
     *
     * @param source this is the stream to read the document with
     * @return this is used to return the event reader implementation
     */
    public EventReader provide(InputStream source) throws Exception {
        return provide(new InputSource(source));
    }

    /**
     * This provides an <code>EventReader</code> that will read from
     * the specified reader. When reading from a reader the character
     * encoding should be the same as the source XML document.
     *
     * @param source this is the reader to read the document with
     * @return this is used to return the event reader implementation
     */
    public EventReader provide(Reader source) throws Exception {
        return provide(new InputSource(source));
    }

    /**
     * This provides an <code>EventReader</code> that will read from
     * the specified source. When reading from a source the character
     * encoding should be the same as the source XML document.
     *
     * @param source this is the source to read the document with
     * @return this is used to return the event reader implementation
     */
    private EventReader provide(InputSource source) throws Exception {
        DocumentBuilder builder  = factory.newDocumentBuilder();
        Document        document = builder.parse(source);
        Location        location = null;
        if (document instanceof DocumentImpl) {
            location = ((DocumentImpl) document).location;
        }
        return new DocumentReader(document, location);
    }
}
